Trip mechanism



July 18, 1950 N. F. BROWN 2,515,291

TRIP MECHANISM Filed Aug. 11, 1947 v M/Vi/VTOZ NORMA/f F BROWN Patented July 18, 1950 Application August 11, 1947, Serial No. 767,947 In Great Britain July 4, 1946 Section 1, Public Law 690, August 8, 1946 Patent expires July 4, 1966 3 Claims.

This invention relates to trip mechanism of the kind wherein a lever or arm is held by an abutment or latch device when the mechanism is set and is adapted to be actuated by spring means when the lever or arm is displaced to release it from the abutment or latch device.

, It is an object of the present invention to provide an improved form of trip mechanism having means whereby theengagement and disengagement of the mechanism from the abutment or latch device is efiected in a rapid and substantially frictionless manner thereby increasing the sensitivity of the mechanism.

According to the present invention the trip mechanism comprises a spring-actuated pivoted triplever provided with a roller adapted to be positioned beneath a fixed abutment to hold the lever in set position with the actuating spring in stressed condition, the trip lever being released by displacing the roller relatively to the fixed abutment till the dead centre of the roller is past the outer edge of the abutment. The lever is pivotally supported on a member which is directly actuated by the spring and the roller is mounted on the lever in anti-friction bearings. To enable the invention to be fully understood it will now be described with reference to the ac companying drawings, in which:

Fig. 1 is a sectional elevation of trip mechanism according to one embodiment of the invention, and

Fig. 2 is a fragmentary sectional side elevation taken at right angles to Fig. 1.

As shown in the accompanying drawing a casing I is provided having a sleeve 2. A coil spring 3 is located in the annular space between the casing I and sleeve 2 and its upper end abuts a flange of an annular member 4. The member 4 is provided with a cross bar 5 which reciprocates in slots in the sleeve 2 and carries a projection 6 formed with a ball-shaped free end I. A trip lever is provided comprising spaced parallel plates 8 connected at the upper end by a cross piece 9 having a concave recess ID to receive the ballshaped end I of the projection 6 whereby the trip lever is pivotally supported. The opposite end of the lever has a roller Il mounted between the plates 8 on a spindle I2 in anti-friction bearings I3. An abutment I4 extends from the sleeve 2 and the roller II is adapted to be positioned beneath this abutment to hold the trip mechanism in set position.

The crosspiece 9 at the upper free end of the lever has shoulders I5, I51: upon which rest the arms I6, I! of a fork provided with an extension I8 having a ball-shaped free end which engages in a bearing recess in the underface of a piston I 9, which is reciprocably mounted in a cylinder 20 formed in the casing l. The cylinder 20 is provided with a bore 2| adapted to be connected with a conduit (not shown). A rod 22 extends into the cylinder 20 through a suitable gland, the upper end of the rod being adaptedto engage with a valve 23 urged on to its seat 24 by a coil spring 25.

As shewn in the drawing, the trip mechanism is in set position with the roller II engaged beneath the abutment l4, and the upper face of the piston I9 spaced from the rod 22 and the valve 23 urged on to its seat 24 by its spring 25.

The trip lever may be released by any suitable means but as shewn in the drawing it is adapted to be released by a rod 28 connected with a-flexiblev diaphragm 21 which is located in an eduction oil pipe 28 of oil pumping apparatus, such as described in British application No. 21,800/46,

The diaphragm is located in a constriction in the pipe 28 and the diiierential pressure set up by flowing oil is adapted to force the diaphragm 2'! inwardly and actuate the rod 26 to engage and displace the trip lever to move the roller I I until its dead centre is past the outer edge of the abutment I4, whereupon the roller will roll over the edge to release the trip and allow the trip lever to be forced upwards by the spring 3. The upward movement of the lever by the spring will also lift the fork I6, I! resting thereon to raise the piston I9, and the rod 22 will accordingly be actuated to lift the valve 23 off its seat 24.

To reset the trip mechanism fluid pressure is supplied to the cylinder 20 by the conduit 2I to force the piston I9 downwardly to depress the fork and lever against the action of the spring 3.

When the lever is in released position, the roller II will rest against the outer face of the abutment I4 and accordingly the lever will be displaced laterally from the central longitudinal position, as shewn in the drawings, and as a result the shoulder I5 will be lowered and out of engagement with the adjacent arm I6 and the shoulder I5a raised and in engagement with the arm IT. The force exerted by the piston I9 to force the trip lever downwardly will accordingly be transmitted only by the arm I I to the shoulder I5a and the force will therefore be applied along a line spaced laterally of and to one side of the longitudinal centre line of the trip lever. A resultant side thrust will accordingly be set up and the lever will be moved axially and also laterally towards the abutment I4, and the roller II will automatically snap under the abutment when the trip lever has been moved downwardly sufiiciently.

It will be understood that when the trip has been set, the supply of fluid pressure will be shut off and the conduit connected with the bore 2| opened to exhaust, to relieve the pressure in the cylinder 20.

In the arrangement here shown, an adjustable spring 33 may be provided in order to predeterminea minimum thrust from the diaphragm 21 necessary to actuate the trip so that it will not be prematurely actuated. Manual operation of the trip mechanism may be provided for either by an extension of the spindle 29 or by an extension of a spindle 26a through suitable glands, the spindle 29 being adapted to be pulled out, and the spindle 260. being adapted to be pushed in by hand against the thrust of spring 33 to release the trip lever.

The roller .ll being freely rotatable provides trip mechanism which is substantially frictionless in operation. Further, it is not necessary,

when releasing the trip, to displace the lever the whole or the roller 1 I is freed from the edge of the abutment; the roller will roll over the edge when its dead centre position has passed the edge of the abutment. Ihe mechanism has accordingly the important advantage thatonly a very small force is required to 'operate it to release the trip. lever, and that that .force can be conveniently determined by adjusting the compression of a spring.

Although the trip lever has been described as opening a valve when released, it may be adapted for actuating any desired form of mechanism. The trip mechanism is particularly adapted for use in oil well apparatus of the kind described in British application No. 21,800 of 19.46 :but is not, however, limited in this respect.

I claim:

. 1. Trip mechanism comprising a support, a trip lever including a pair of connected parallel spaced arms, means for pivotally mounting said arms on said support, a roller mounted between said arms at a point remote from said pivotal mounting, a fixed abutment extending between said arms for engagement by said roller to hold the trip lever in set position and spring means held in a loaded condition when the said lever is set and operative to actuate said arms when said roller is released from engagement with its said abutment and means actuated by fluid pressure for moving said trip lever to disengage said roller from engagement with said abutment.

'2. Trip mechanism comprising a casing, a cylindrical recess in said casing, a piston in said recess, a support reciprocably mounted in said casing beneath said piston, spring means connected with said support normally urging it towards said piston, a trip lever pivoted at one end to said support, a roller mounted on said trip lever at a position spaced from the said pivoted end, means connecting said lever and piston, a fixed abutment extending inwardly of said casing for engagement by said roller to hold the said trip lever in set condition stressing said spring means, said spring means being operative to raise the said support and the said trip lever and piston connected therewith when the roller is released from its abutment and means for supplying fluid pressure to said cylindrical recess in the casing to actuate the piston to move the support and trip lever downwardly to reset the trip mechanism.

3. Trip mechanism comprising a casing, a cylindrical recess in said casing, a piston in said recess, a support reciprocably mounted in said casing beneath said piston, spring means connected with said support normally urging it to wards said piston, a trip lever pivoted at one end to said support, a roller mounted on said trip. lever at a position spaced from the said ivoted. end, means connecting said lever and piston, .a'

fixed abutment extending inwardly of said casing for engagement by said roller to :hold the said trip lever in set condition stressing said springmeans, said spring means being operative to raise;

the said support and the said trip lever and piston connected therewith when the roller is released from its abutment and means for supplying fluid pressure to said cylindrical recess the casing to actuate the piston to move the support and trip lever downwardly to resetthe trip m'echanism and means for derivingwa lateral thrustfrom the said downward thrust .as the said lever-1 is moved downwardly by the said piston, autosmatically to re-engage the said roller with said abutment to reset the trip mechanism.

NORMAN FRASER. BROWN.- I.

REFERENCES GT-TED The following references are of record in file of this patent:

UNITED STATES PATENTS Name Date 224,254 339,043 956,595 1,030,532 1,271,964 1,532,212 1,782,664 1,974,844 2,454,189

Coffee Mar. 30, 1886 Pederson Jan. .25, 19-12 Roe Nov. 25, 19.30

Warne Feb. 3, 1380' McKee May 3, 1919,

Wald-ow July 9, 1918. Wilms s Apr. 7, 1925 Cartwright Sept. 25, 19.34 Lentjes Nov. 16, 1948, 

